Should I go through ADU permit process for an attached suite?

[Hallie Mel]

I just closed on a house with a master suite that I'm planning to rent out. The suite is a fully permitted converted garage (this was done decades ago) with a permitted utility room, and separate door to backyard. I'm planning to swap out the washer/dryer for a kitchenette, install a sturdier door between it and the rest of the house (or wall it off entirely) and that's pretty much it. I will be living in the rest of the house, and would rather not split the utilities. Is an ADU permit necessary or wise in this situation, and how much would it cost given the lack of new construction? I anticipate undoing the kitchen/door changes before selling the house.